Docs: mention clan.nix file, which is present in the default template now

docs/site/guides/getting-started/add-machines.md

@@ -90,6 +90,7 @@ See the complete [list](../../guides/more-machines.md#automatic-registration) of
     The option: `machines.<name>` is used to add extra *nixosConfiguration* to a machine
 
 ```{.nix .annotate title="flake.nix" hl_lines="3-13 18-22"}
+# Sometimes this attribute set is defined in clan.nix
 clan = {
     inventory.machines = {
         jon = {

docs/site/guides/getting-started/add-services.md

@@ -28,6 +28,7 @@ To learn more: [Guide about clanService](../clanServices.md)
         inputs@{ flake-parts, ... }:
         flake-parts.lib.mkFlake { inherit inputs; } {
             imports = [ inputs.clan-core.flakeModules.default ];
+            # Sometimes this attribute set is defined in clan.nix
             clan = {
                 inventory.machines = {
                     jon = {
@@ -76,6 +77,7 @@ Adding the following services is recommended for most users:
         inputs@{ flake-parts, ... }:
         flake-parts.lib.mkFlake { inherit inputs; } {
             imports = [ inputs.clan-core.flakeModules.default ];
+            # Sometimes this attribute set is defined in clan.nix
             clan = {
                 inventory.machines = {
                     jon = {

docs/site/guides/getting-started/secrets.md

@@ -152,6 +152,7 @@ are loaded when using Clan:
   outputs =
     { self, clan-core, ... }:
     let
+      # Sometimes this attribute set is defined in clan.nix
       clan = clan-core.lib.clan {
         inherit self;